Boom retracting machinery



Feb 11, 1969 c. F. NoyoTNY `3,426,916

BOOM RETRACT ING MACHINERY Filed June 29, 1967 sheet of 2 LOAD-(1Nloo,ooo INCH Les.)

0 20 4o 0. 'o 7.00 /2'0 4 lo [8o ROTATIONUN DEGREES) INVENTOR CARL E.NovoTNv ATTORNEY Feb-11, 1969 C F, .NOVOTNY 3,426,916

BOOM RETRACTING MACHINERY Filed Juneze, 1967 sheetv 2 om lNvENToR CARLF. NovoTNv AT TORNEY United States Patent 6 Claims ABSTRACT F THEDISCLOSURE The bifurcated foot of the boom of a truck mounted crane ispivotally attached to respective outer ends of parallel retracting arms,the inner ends of which are fulcrumed on the revolving frame andconnected by a torque shaft. The arms a-re pivotal through 180 to liftand move the boom foot between a retracted position to the rear of theframe and a forward working position. An actuating lever for the armshas an inner end fulcnlmed on the fra-me below the fulcrum of the armsand an outer end which has a pin and slot connection with one arm. Ahydraulic actuator cylinder is connected between the frame and amidpoint of the lever and is operable to reciprocally pivot the leverand, therefore, the arms.

Background of the invention It is desirable in a truck mounted crane orthe like to be able to retract the boom to shorten the machine fortravel purposes. The copending application of George W. Mork, Ser. No.600,541, tiled Dec. 9, 1966, discloses an embodiment of a truck mountedcrane with a retractable boom in which the boom foot is connected to theouter ends of actuating arms which are fulcrumed on the re- `volvingframe. The arms are pivotal through 180 to lift and move the boom footbetween a forward working position and a retracted position to the rearof the frame.

The general arrangement shown in the aforesaid Mork application is verysatisfactory from the standpoint of simplicity and strength, but it isdifficult to provide suitable lmeans for pivoting the arms. The primaryproblem in this regard is the variability of the torque load as the boommoves from one position to the other. During retraction, for example,the arms pivot between positions in which they extend horizontallyforward and horizontally rearward. Since the boom foot is supported atthe ends of the arms, the torque load begins at a maximum, goes to zeroas the arms pass through vertical and then again becomes a maximum.Further, the torque load changes from positive to negative as the armspass through vertical. Because of the dramatic changes in degree andcharacter of the torque load, it is extremely ditiicult to provide aneicient actuating means to pivot the arms.

Summary of the invention The boom retracting machinery of this inventionprovides a turning block linkage for retracting and extending the boom.The retracting arms form one moving link, and an actuating lever formsthe other moving link, the outer end of the actuating lever having alost motion or sliding block connection with one of the arms. Thefulcrum of the actuating lever is below the fulcrum of the retractingarms so that it is required to move through substantially less angulardistance as the arms move through 180 As a result, it is possible to usea single conventionally mounted hydraulic cylinder as an actuator. Notonly does the machinery of the invention allow for an extremely simplebut strong apparatus, but its torque capability matches the torque loadalmost exactly.

3,426,916 Patented Feb. l1, 1969 ICC Brief description of the drawingsFIG. 1 is a fragmentary schematic view of a truck mounted crane lwiththe boom retracting machinery of this invention incorporated therein,the elements being shown in a working position with an intermediateretracting position being shown in broken lines,

FIG. 2 is an enlarged fragmentary side view of the apparatus of FIG. 1,but with the elements shown in a fully retracted position,

FIG. 3 is an enlarged fragmentary top view similar to FIG. 2 and furtherillustrating the elements shown therein, and

FIG. 4 is a graph showing torque capability and load curves for themachinery of FIGS. 1-3.

Description of the preferred embodiment The numeral 1 n t-he drawingsdesignates the revolving frame of a truck mounted crane, only a portionthereof being shown, and the numeral 2 designates a generallyconventional `boom lmounted thereon. As can be seen in FIG. 3, the footportion of the boom 2 is bifurcated to define two spaced, rearwardlyextending parts 3. The ends of the parts 3 are pivotally connected at 4to the respective outer ends of parallel retracting arms 5, the points`l serving not only as points of connection, but also servin-g to denethe actual foot of the boom 2.

A pair of laterally spaced, upstanding supports 6 are provided on theframe 1, and -a transverse tubular torque shaft 7 is journaled therein.The inner ends of the retracting arms 5 are fixed to the respective endsof the tube 7 to pivotally mount them on the frame 1, with the center ofthe tube 7 deiining a fulcrum for the arms 5.

Obvious additional elements of the truck mounted crane such as thecarrier vehicle, hoist machinery, etc. are not fully shown and describedherein since they are well known to those skilled in the art and art notnecessary per se to the invention herein. A specific illustrativeshowing of such a crane, and a showing of a retractable boom of theIgeneral type contemplated herein, can be found in the aforementionedcopending application of George W. Mork, Ser. No. 600,541.

`One of the supports 6, the one to the front in FIGS. l and 2 and belowin PIG. 3, also suitably pivotally mounts and denes a fulcrurn I8 forthe inner end of an actuating lever 9, the fulcrurn l8 being outside,below and just slightly behind the fulcrum 7 of the arms 5. Theactuating lever 9 is pivotal in a vertical plane adjacent and parallelto the plane of pivotal movement of the nearest arm 5. The outer end ofthe lever 9 is provided 'with a transverse pin 10 which is received andmovable in a longitudinally extending slot 11 formed in the associatedarm 5, the pin 1 0 and slot 11 defining a lost motion or sliding blockconnection between the outer end of the lever 9 and the associated arm5, which connection is at any suitable midpoint, i.e., point between theends, of the arm 5.

A conventional two-way hydraulic actuator cylinder 12 of suitable formis pivotally connected at one end 13 to the frame 1 and has its otherend pivotally connected to the lever 9 at a suitable midpoint 14.Extension and retraction of the cylinder 12 will cause the lever 9 topivot reciprocally in a vertical plane about its fulcrum 8, thetransverse pivotal connections 13 and 14 allowing the cylinder 12 tomove vertically as required. Because of the connection afforded by thepin 10 and slot 11, the lever 9 'will in turn cause the arms 5 to pivot.about their fulcrum 7 to move the boom foot `4. The lever 9' acts onlyon the nearest arm S of course, but the torque shaft 7 transmits itsforce substantially equally to the far arm 5.

As a result of having the shaft 7, it is unnecessary to provide twolevers 9 and actuating cylinders 12.

The full line showing f FIG. 1 illustrates what is termed a workingposition in which the boom foot 4 is at the forward end of the frame 1and the arms S are horizontal and extend forwardly from their fulcrums7. In this position, the lever 9 extends upwardly and forwardly from itsfulcrum 8 and the cylinder 12 is fully retracted. During working, theboom foot 4 will of course be suitably locked in place, and the boom 2may be lulfed in the usual fashion.

When it is desired to retract the boom 2, it is first fully lowered tothe horizontal position shown in FIG. 1 wherein a guiding and supportingwheel 15 provided on the tip of the boom 2 rests on the ground. Thecylinder 12 is then extended to cause counterclockwise pivoting of thelever 9 and arms 5, the elements then moving through the intermediateposition shown in broken lines in FIG. 1 to the position shown in FIG. 2which is termed a retracted position. In retracted position, the boomfoot 4 is at the rear of the frame 1 and the arms 5 are horizontal andextended rearwardly from their fulcrum 7, the lever 9 extends upwardlyand rearwardly, and the cylinder 12 is fully extended. As the elementsmove from working to retracting position, the pin 10 moves from theouter end of the slot 11 to the inner end and then back again to theouter end, thus providing a lost motion connection which compensates forthe difference in elevation of the fulcrums 7 and 8. Having the fulcrum8 offset behind the fulcrum 7 insures against a dead spot when the arms5 reach a vertical position. The same effect could of course be had byoffsetting the fulcrum 8 forwardly.

As the boom 2 is retracted, the foot 4 moves in a semicircle, and as aresult the initial and final phases of its movement are largely verticalwith the major horizontal movement occurring between. During the firstphase of movement, the boom foot 4 is lifted quickly, and this insuresthat the underside of the boom 2 will clear the `forward edge of theframe 1 during much of the retracting movement. As the boom 2 movesbackward during this portion `of the process, much of its weight iscarried -by the wheel 15 which rolls along the ground. As illustrated bythe broken line showing in FIG. l, when the arms 5 are vertical theunderside of the boom 2 is spaced substantially above the frame 1. Atsome point after the arms 5 pass vertical so that the foot 4 begins tomove down, however, the underside of the boom 2 will be moved down farenough to come against the forward edge of the frame 1, and rollers 16are provided on the frame 1 and are positioned to engage the undersideof the boom 2 at this point. When the boom 2 is against the rollers 16,further rearward and downward pivotal movement of the arms 5 will causethe boom 2 to pivot about and roll rearwardly on the rollers 16, and theweight of the boom 2 will be shifted from the wheel 15 to the rollers16, the wheel 15 then being lifted off the ground.

rlhe curve 17 shown in FIG. 4 reflects the torque load on the boomretracting machinery shown during a movement from working to retractedposition, this load being of course primarily the result of the weightof the boom 2 which is approximately 4500 pounds in this embodiment. Atthe beginning of a retracting action, the load is maximum in degree andis positive -or clockwise in character. When the load is positive,pushing force by the cylinder 12 is required to effect movement. Thepositive torque load gradually decreases in degree as the arms 5 pivotupwardly toward a vertical position and reaches zero at the point 18where they are fully vertical. As soon as the arms 5 pass throughvertical, the torque load changes from positive or clockwise to negativeor counterclockwise, and at this point the cylinder 12 assumes a holdingfunction. (For the sake of clarity, the torque load curve after the zeropoint is passed is shown in FIG. 4 as being above the abscissa in FIG.4, but it is drawn in broken lines to indicate that it is negative incharacter.) As the arms 5 move further, from vertical to fully retractedposition, the load gradually increases again in degree. At a pointmarked 19, however, the boom 2 comes against the rollers 16, and at thispoint the load instantly goes back to positive, a pushing force by thecylinder 12 being required to pivot the boom 2 onto the rollers 16. Thisis shown by the phantom vertical line leading upwardly from the point19, the continuation of the curve 17 from this line being shown as afull line to indicate its positive character.

The curve 20 in FIG. 4 defines and illustrates the torque capability ofthe boom retracting mechanism shown, assuming a ve inch cylinder with atwo inch piston operated at 2000 p.s.i. The system capability, it willbe seen, is also at a maximum when the elements are in working position,decreases to a minimum at a point 21 when the lever 9 is vertical andincreases again to a maximum when the elements are in retractedposition. The output capability of the system also changes from positiveto negative at the point 21 and goes back to positive at a point 22corresponding to the point 1-9, the cylinder 12 changing from pushing topulling functions and back through suitable circuitry known to thoseskilled in the art. The minimum point 21 of the curve 20 and the zeropoint 18 of the curve 17 do not exactly coincide because of the slightrearward spacing of the fulcrurn 8 from the fulcrum 7, but they veryclosely approximate one another. All in all, it will be seen that thecurves 17 and 20 are very similar so that the capability of the systemis very closely matched to the requirements put upon it, and the samewill obviously be true for a movement back to working position. Thisclose matching .provides obvious design advantages in that minimalelements can -be used and no substantial capability or work is wasted.The necessity of pivoting the boom 2 onto the rollers 16 affects thesymmetry of the curves 17 and 20 t-o some extent, but does notsignificantly change the close matching of capability to load, Formovement from retracted to working position or vice versa both the loadand capability, for all practical purposes, begin at a maximum, gothrough zero together and end at a maximum.

The curves 17 and 20 assume certain sizes, weights, and otherconditions. The general relationships shown, however, will obtain evenif these conditions are varied.

It will also be noted from an examination of FIGS. 1 and 2 that whereasthe arms 5 pivot through approximately during a retracting action or areturn to working position, the lever 9 pivots through a substantiallylesser angular distance. This allows for the use of the single xedcylinder 12 as an actuator. If a cylinder were to be attached directlyto the arms 5 to move them through 180, some provision would have to -bemade for moving its point of connection with the frame 1 to allow forthe full 180 movement required.

Although a preferred embodiment of the invention has been shown herein,it will be obvious to those skilled in the art that variations in thestructure shown can be made without departure from the concept of theinvention. Further, the invention is not limited in possible use totruck mounted cranes and other applications are obviously feasible. Inview of the .possible variations in both structure and use, theinvention is not intended to be limited by the showing herein or in anyother manner except insofar as limitations appear specically in thefollowing claims.

I claim:

1. In a truck mounted crane or the like having a revolving frame, aretracting arm having an inner end fulcrumed on the frame and an outerend, and a boom having a foot pivotally connected to the outer end ofthe retracting arm, the combination therewith of: an actuating leverhaving an inner end fulcrumed on the frame at a point below the fulcrumof the actuating arm and an outer end connected to a mid-point of theactuating arm with a lost motion connection; and an actuator connectedbetween the frame and a midpoint of the actuating lever, the actuatorbeing operable to reciprocally pivot the actuating lever to in turncause reciprocal pivotal movement of the actuating arm.

2. The combination of claim 1 wherein the actuator comprises a two-wayhydraulic cylinder with transverse pivotal connections at its ends tothe frame and actuating lever.

3. The combination of claim 1 wherein there are two parallel retractingarms and the boom foot is bifurcated with its two parts connected to theouter ends of respective arms; and wherein there is a transverse torqueshaft connecting the inner ends of the arms; and wherein the actuatinglever is connected to only one of the arms.

4. The combination of claim 1 wherein the lost motion connection betweenthe outer end of the actuating lever and the arm comprises alongitudinal slot provided in the arm and a transverse pin at the outerend of the actuating lever this is received and movable in the slot.

5. The combination of claim 1 wherein the fulcrum of the lever is offsetfrom the fulcrum of the arm to prevent a dead spot as the arms gothrough vertical.

6. The combination of claim 1 wherein the actuator comprises a two-wayhydraulic cylinder with transverse pivotal connections at its ends tothe frame and actuating lever; and wherein there are ltwo parallelretracting arms and the boom foot is bifurcated with its two partsconnected to the outer ends of respective arms; and wherein there is atransverse torque shaft connecting the inner ends of the arms; andwherein the actuating lever is connected to only one of the arms; andwherein the lost motion connection between the outer end of theactuating lever and the arms comprises a longitudinal slot provided inthe arm and a transverse pin at the outer end of the actuating leverthat is received and movable in the slot; and wherein the fulcrum of thelever is otset from the fulcrum of the arm to prevent a dead spot as thearms go through vertical.

FOREIGN PATENTS 1,214,066 11/1959 France.

HUGO O. SCHULZ, Primary Examiner.

U.S. Cl. X.R. 2. l2-7O jgg@ UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3, 426, 916 Dated February 11, 1969 Inventor s)Carl F., Novotny It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 4, line 75, "actuatingH should be retractng Column 5, line l,"actuating" should be retractin Column 5, line 6, "actuating" Should beretracting Signed and sealed this 3rd day of April 1973.

(SEAL) Attest:

EDWARD'M.FLETCHER,JR. ROBERT GOTTSCHLK Attestlng Officer Commissioner ofPatents

